FreePort Express is a binary translator (running on Alpha) which permits
you to convert your SunOS 4.1.x (same as Solaris 1.x) user executables
into Digital UNIX executables in minutes. FreePort Express runs under
Digital UNIX V3.0 or later, and is available FREE of charge (hence the name).

FreePort Express can handle the translation if your executable is:
SunOS 4.1.x
user mode
not priviledged
is a valid a.out

Things it won't handle:
programs which rely upon SunOS file system hierarchy or file
formats where such differ from those in Digital UNIX
uses SunView
is a driver
broken code

How fast is the translated code?
At SunWorld '95, we showed some translated programs running
side by side on equally configured, similarly priced machines:
a SPARCstation 20/71, and an AlphaStation 400 4/233.
In all cases, the translated programs ran as fast as, or faster
than the originals programs did.